Subscribers use mobile stations to conduct voice communications. Also, data communications, along with other enhanced capabilities of wireless communications systems, are also being provided in these mobile networks. Thus, it has become desirable for many subscribers to be able to use their mobile station as a primary communication device. In many situations, it has not been possible to replace the line-based telephone system in a building because of an inability to achieve sufficient radio frequency communications from inside the building to wireless communication network equipment located outside.
There are RF losses associated with signals trying to penetrate through walls, for example. Concrete, steel, and other building materials block cellular signals, so even when coverage from the macro cell penetrates the building, the signal may be weak or nonexistent in some areas. In many locations, the signal does not have sufficient quality because of conflicting signals from multiple macro cells that happens in cell borders, typically when a handover is initiated, which cause many devices to continually hunt between one source and another. Moreover, macro cells sometimes have capacity limitations due to demand from other users in the area, which can lead to blockages and longer call setup times.
With proliferation of consumer operated IEEE 802.11 wireless data networks, such as Wi-Fi® one option for expanding wireless communication capability is to provide signaling devices within buildings to supplement conventional communications to allow use of a mobile station in a more reliable manner within the building. For example, base station router devices may be used within buildings for interfacing between a mobile station and a wireless communication network so that a subscriber achieves reliable communications within small area.
Femto cell access points are individual radios, essentially small versions of the cellular base stations that provide limited coverage for mobile devices. Femto cells typically have low output power, limited capacity, and are designed for small spaces like apartments or houses. Femto cell products look like Wi-Fi access points and connect to an IP network for backhaul transport. Like the management switch that regulates traffic from the multiple access points in a wireless LAN, femto cell systems manage the flow of traffic out to each cell and back, from the in-building network to the carrier's broader network.
Home or small area WCDMA coverage for limited number of users can be provided using a small radio base station (“RBS”), also called a “femto RBS” and/or a “Home RBS.” According to such investigation, the small RBS would provide normal WCDMA coverage for the end users (e.g., to a user equipment unit (UE)), and would be connected to the RNC using some kind of IP based transmission. The coverage area so provided is called a “femto cell” (to indicate that the coverage area is relatively small). Other terminology for a femto cell includes “pico cell” or “micro cell”, which is in contrast to a macro cell covered by a macro or standard radio base station (RBS).
One alternative for the IP based transmission is to use Fixed Broadband access (like xDSL, Cable etc.) to connect the home RBS to the RNC. Another alternative would be to use Wireless Broadband access (e.g. HSDPA and Enhanced Uplink; or WiMAX). Two different backhaul alternatives include “xDSL Backhaul” and “WiMAX Backhaul,” as described in greater detail below.
A femto RBS is typically installed by the end user rather than the network operator. The end users are also able to move the femto RBS geographically from place to place without the operator being able or willing to control relocation of the femto RBS. Such user-directed relocation requires that, wherever the femto RBS is installed or located, it should connect to the correct RNC.
With a proliferation of such base station router devices, various challenges become apparent. One issue that may arise is false handover where a mobile station is handed over from a serving macrocell to an incorrect base station router device (e.g., a femtocell home unit). A cell may be considered a macrocell, for example, if it is served by a base station and includes other base stations of limited coverage area within the region of the macrocell. Some such devices are referred to as base station router devices that essentially cover a femtocell cell range within a macrocell (e.g., within a building or floor).
With several femtocells within a geographic area, the possibility for false handovers exists. Any attempt to minimize such false handovers should be done with a minimum requirement for processing and signaling to avoid adding burden to the wireless communication system. For example, if a radio resource control layer of the system is required to address false handover situations, additional network signaling and delays in executing correct handovers will be introduced. This becomes especially true when there are large numbers of mobile stations regularly attempting false handovers. Thus, there is a need to minimize or avoid false handovers.